What zone 8a means for Washington
Hardiness zones are based on the average of the coldest night of each winter over 30 years (1991 to 2020). In zone 8a, that average is 10 to 15°F (-12 to -9°C). Plants labeled hardy to zone 8a or colder should survive a typical Washington winter. A plant rated only to a warmer zone will need a sheltered spot, a pot you can bring inside, or treating as an annual.
Not every part of Washington is the same: its ZIP codes fall in zones 7b, 8a. Check your own ZIP code in the table below.
How Washington compares with the rest of District of Columbia
District of Columbia runs from zone 7b to zone 8a on the 2023 map. About 86% of the state's ZIP codes share Washington's zone 8a. Washington is in the warmest zone found in the state.
Frost dates in Washington
These are the median dates of the last and first 32°F freeze from NOAA's 1991 to 2020 climate normals, using the weather station closest to Washington (National Arboretum DC, about 2 km away). Half of years have a later last frost, so tender plants are safest a week or two after the date. Your own garden can differ with elevation and shelter: check your exact ZIP code above.
Vegetable planting calendar for Washington
Purdue Extension groups vegetables by how much frost they can take and times planting from the average last spring frost. Applied to Washington's last frost of March 29:
| Group | Plant outdoors | Crops |
|---|---|---|
| Hardy crops (tolerate a hard frost) 4 to 6 weeks before the average last spring frost | February 15 to March 1 | Asparagus, broccoli, Brussels sprouts, cabbage, collards, horseradish, kale, kohlrabi, leek, mustard, onion, peas, potato, radish, rhubarb, spinach, turnip |
| Semi-hardy crops (tolerate a light frost) 2 to 4 weeks before the average last spring frost | March 1 to March 15 | Beet, carrot, cauliflower, celery, chard, Chinese cabbage, lettuce, mustard, parsnip |
| Tender crops (damaged by frost) after the average last spring frost, once nights stay above 50°F | From March 29 | Bean, sweet corn, tomato |
| Very tender crops (warm season) at least 2 weeks after the average last spring frost, once nights stay above 60 to 65°F | From April 12 | Cucumber, eggplant, melons, okra, pepper, pumpkin, squash, sweet potato |
Spring planting for direct seeding or transplants. A late cold snap can still happen, so watch the forecast and protect tender plants. Want today's answer for your ZIP code? Use what to plant now.
Sources: NOAA NCEI U.S. Climate Normals 1991 to 2020; Purdue Extension, Indiana Vegetable Planting Calendar (HO-186-W).
Choosing plants for zone 8a
When you shop, look for the hardiness range on the tag or in the catalog, such as "zones 4 to 9". Pick perennials, shrubs and trees whose range includes 8a. If you are set on a plant rated only to a warmer zone, plant it in a sheltered spot against a south-facing wall, mulch the roots before winter, or grow it in a container you can move into a garage. Zones only cover winter cold, so also check sun, water and soil needs. More in how to read a plant tag.
Washington ZIP codes and zones
ZIP codes GeoNames assigns to Washington, which can include PO box ZIP codes.
Frequently asked questions
When is the last frost in Washington?
The median last spring frost (32°F) near Washington is March 29, and the median first fall frost is November 8, based on NOAA 1991 to 2020 climate normals.
What planting zone is Washington in?
Washington, DC is in USDA plant hardiness zone 8a (ZIP codes range from 7b to 8a). Zone 8a means an average coldest winter night of 10 to 15°F (-12 to -9°C), based on the 2023 USDA map.
Did Washington's zone change in 2023?
The 2023 USDA map uses weather data from 1991 to 2020. The USDA says about half of the country shifted to the next warmer half zone compared with the 2012 map, while the rest stayed in the same half zone.
Zones: 2023 USDA Plant Hardiness Zone Map ZIP code listings, PRISM Climate Group, Oregon State University. Place names: GeoNames (CC BY 4.0). Not the official USDA map. Our data.